mc_pos_control: always require takeoff setpoint
mc_pos_control: always require takeoff setpoint

Problem: The drone started taking off in LOITER (HOLD) mode even if on
ground and did not do a proper takeoff jump. The effect was mostly a
hovering close above ground or tilting/flipping because of integrator
wind-up.

Solution: Stay at minimum throttle until a takeoff setpoint is issued.

krbeverx/Firmware,dagar/Firmware,mje-nz/PX4-Firmware,mje-nz/PX4-Firmware,jlecoeur/Firmware,jlecoeur/Firmware,krbeverx/Firmware,Aerotenna/Firmware,Aerotenna/Firmware,PX4/Firmware,mcgill-robotics/Firmware,PX4/Firmware,acfloria/Firmware,acfloria/Firmware,PX4/Firmware,Aerotenna/Firmware,dagar/Firmware,PX4/Firmware,jlecoeur/Firmware,dagar/Firmware,krbeverx/Firmware,jlecoeur/Firmware,mcgill-robotics/Firmware,Aerotenna/Firmware,jlecoeur/Firmware,dagar/Firmware,acfloria/Firmware,mje-nz/PX4-Firmware,krbeverx/Firmware,Aerotenna/Firmware,krbeverx/Firmware,acfloria/Firmware,PX4/Firmware,mcgill-robotics/Firmware,jlecoeur/Firmware,mje-nz/PX4-Firmware,PX4/Firmware,mcgill-robotics/Firmware,dagar/Firmware,Aerotenna/Firmware,dagar/Firmware,jlecoeur/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,acfloria/Firmware,acfloria/Firmware,mje-nz/PX4-Firmware,dagar/Firmware,acfloria/Firmware,mcgill-robotics/Firmware,mcgill-robotics/Firmware,Aerotenna/Firmware,krbeverx/Firmware,mje-nz/PX4-Firmware,mcgill-robotics/Firmware,PX4/Firmware,jlecoeur/Firmware